This is MORNING EDITION from NPR News. Good morning. I'm David Greene.

RENEE MONTAGNE, HOST:

And I'm Renee Montagne.

Yesterday on Capitol Hill, an extraordinary fight went public between a senator and the CIA. California Democrat Dianne Feinstein accused the agency of snooping on computers used by the staff of the Senate Intelligence Committee - which she chairs. Here's Senator Feinstein on the Senate floor yesterday.

SENATOR DIANNE FEINSTEIN: I have asked for an apology and a recognition that this CIA search of computers used by its Oversight Committee was inappropriate. I have received neither.

MONTAGNE: The dispute centers on the CIA's role in the use of harsh interrogation techniques on detainees after the 9/11 attacks and a Senate report that describes those practices.

NPR's Carrie Johnson is here this morning to discuss the controversy. Good morning.

CARRIE JOHNSON, BYLINE: Good morning, Renee.

MONTAGNE: Now, help us unravel what is a many layered story. What is at the core of the dispute between the CIA and the Senate Intelligence Committee?

JOHNSON: Renee, this is really about a 6,000 page report on CIA detention and interrogation practices from 2002 to 2009, which Senate aides say sets out in chilling and brutal details what the U.S. did to terrorism suspects after 9/11. A Senate aide spent years reviewing millions of pages of documents in a secure location in Virginia to prepare this report.

And Senator Feinstein yesterday finally said the CIA has been stonewalling, and she in fact accused the agency of interfering or thwarting that Senate investigation.

Now, it's important to note, Renee, CIA director John Brennan says the agency did no such thing. He believes the agency has been cooperating with the Senate but the Senate report simply has some major facts wrong and key points wrong. The draft report, though, is still under wraps, it needs to ultimately be sent to the White House for declassification.

MONTAGNE: Now, Carrie, Senator Feinstein is generally a huge supporter of the national security and intelligence community. She's backed the CIA on drones and surveillance. So how did this relationship go so bad?

JOHNSON: Yeah. Renee, this is big. This is big and bad news for the CIA. Senator Feinstein is maybe the chief ally of the administration and her decision to go public with all of this demonstrates the real lack of trust. The senator talked about documents that were provided to the committee and vanished - her complaints to the White House early in the administration. And she even brought up how the CIA destroyed videotapes that depicted some of this, what she perceives as torture, back in 2005. And she said this all came to a head because important documents started vanishing again and she was concerned that the CIA might tamper with them. So her aides took those documents to a secure location in a Senate office building and then the CIA found out and told lawmakers they had searched the computers at that secure site in Virginia.

MONTAGNE: So the Senate is supposed to be overseeing the CIA and now we have the CIA allegedly spying on the Senate - that's what Senator Feinstein said.

FEINSTEIN: I have grave concerns that the CIA's search may well have violated the separation of powers principle embodied in United States Constitution.

JOHNSON: Exactly, Renee. The senator seem particularly concerned that the CIA had asked the Justice Department to look into the activities of her Senate aides.

MONTAGNE: And what is the CIA director saying about this, briefly?

JOHNSON: The CIA director, John Brennan, said he wants senators to slow down, take their time and let these accusations sort themselves out with the investigation. He says he's happy to talk to the White House when this is all over about what he did or didn't do, and the president should decide what should happen. The CIA has a lot on its plate, Brennan says, and he really wants to put this chapter after 9/11 behind it. You know, he was going to retire after Obama's first term, But he said he couldn't pass up the chance to lead the CIA, where he started working in 1980. So he's really a true believer.